System and methods for t1 and t2 weighted magnetic resonance imaging

ABSTRACT

A magnetic resonance imaging method includes performing an inversion pulse sequence using an MRI system, the inversion pulse sequence producing an inversion recovery period, and during the inversion recovery period: (i) performing a longitudinal T2 encoding pulse sequence using the MRI system; (ii) acquiring a post longitudinal T2 encoding pulse sequence image signal block immediately following the longitudinal T2 encoding pulse sequence using the MRI system; and (iii) acquiring an additional image signal block either before the longitudinal T2 encoding pulse sequence or following the acquiring of the post longitudinal T2 encoding pulse sequence image signal block using the MRI system. The method further include generating calculated image data based on at least the post longitudinal T2 encoding pulse sequence image signal block using a self-correcting normalization image combination scheme.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) from U.S.provisional patent application No. 62/685,366, entitled “System andMethods for T1 and T2 Weighted Magnetic Resonance Imaging” and filed onJun. 15, 2018, the disclosure of which is incorporated herein byreference.

GOVERNMENT CONTRACT

This invention was made with government support under grant #s NS090417,EB024408 and NS081772 awarded by the National Institutes of Health(NIH). The government has certain rights in the invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to magnetic resonance imaging (MRI), and,in particular, to MRI methods, and a system implementing same, thatgenerate T1 and T2 weighted images in a time and specific absorptionrate (SAR) efficient manner, even at 7T.

2. Description of the Related Art

Magnetic resonance imaging (MRI) is a medical imaging technique used toform images of the anatomy of the body. MRI scanners or systems usestrong magnetic fields, electric field gradients, and radio waves togenerate images of the tissue and/or organs in the body. In particular,MRI is based on the magnetization properties of atomic nuclei. Apowerful, uniform, external magnetic field is employed to align theprotons that are normally randomly oriented within the water nuclei ofthe tissue being examined. This alignment is next perturbed by theintroduction of external Radio Frequency (RF) energy. The nuclei returnto their resting alignment through various relaxation processes and, inso doing, emit RF energy. After a certain period following the initialRF, the emitted signals are measured and used to create images.

Each tissue returns to its equilibrium state after excitation by theindependent relaxation processes of T1 (spin-lattice; that is,magnetization in the same direction as the static magnetic field) and T2(spin-spin; that is, magnetization transverse to the static magneticfield). For example, to create a T1-weighted image, magnetization isallowed to recover before measuring the emitted RF signals by changingthe repetition time (TR). To create a T2-weighted image, magnetizationis allowed to decay before measuring the emitted RF signals by changingthe echo time (TE).

Fluid-attenuated inversion recovery (FLAIR) is an MRI sequence with aninversion recovery set to null fluids. For example, it can be used inbrain imaging to suppress cerebrospinal fluid (CSF) effects on theimage.

Currently there is not a good method by which T2 weighted and FLAIRimaging may be acquired at 7T. There are two groups of prior art methodswhich are available, both of which have known problems. The standardmethod is derived from 3T applications, and uses multiple (turbo) spinecho refocusing pulses to acquire multiple lines of data. At 7T,however, the high power demands of the transmit coil to generate themultiple refocusing pulses results in data acquisition being extremelyslow because of limitations in the specific absorption rate (SAR), whichis set by the CDRH (Centers for Devices and Radiological Health) and theFDA. The common method to minimize this effect is to reduce therefocusing angle; however this results in decreasing the image quality.For FLAIR imaging, this problem becomes more acute due to the need formultiple inversion pulses. The second, alternative method is the“variable flip angle” method. However, as several investigative groupshave discussed, the variable flip angle strategy is very sensitive to RFhomogeneity with the apparent T2 relaxation varying with k-spacelocation. Additional approaches based on measured B1+ and paralleltransmit design of individual k-space locations can mitigate thiseffect, however this significantly increases complexity inimplementation. While several studies have found that the fast variableflip angle. TSE gives comparable images to conventional refocusingmethods, the potential need to adjust parameters on a per-applicationbasis will be time consuming. Thus, overall, for many 7T studies, theT2W and FLAIR methods are still performed with the 2-dimensionalsequence, acquired with high in-plane resolution and thick slices (e.g.,0.4×0.4×3.5 mm3).

SUMMARY OF THE INVENTION

In one embodiment, an MRI system is used with a magnetic resonanceimaging (MRI) method that includes performing an inversion pulsesequence followed by a recovery period, and during the recovery period:(i) performing a longitudinal T2 encoding pulse sequence; (ii) acquiringa post longitudinal T2 encoding pulse sequence image signal blockimmediately following the longitudinal T2 encoding pulse sequence; and(iii) acquiring an additional image signal block either before thelongitudinal T2 encoding pulse sequence or following the acquiring ofthe post longitudinal T2 encoding pulse sequence image signal block. Themethod further includes generating calculated image data based on atleast the post longitudinal T2 encoding pulse sequence image signalblock using a self-correcting normalization image combination scheme.

In another embodiment, a magnetic resonance imaging system is providedthat includes a magnet, an RF system, and a control system. The controlsystem stores and is structured and configured to execute a number ofroutines, wherein the routines are structured and configured to performan inversion pulse sequence using the RF system, the inversion pulsesequence producing an inversion recovery period, and during theinversion recovery period: (i) perform a longitudinal T2 encoding pulsesequence using the RF system; (ii) acquire a post longitudinal T2encoding pulse sequence image signal block immediately following thelongitudinal T2 encoding pulse sequence using the RF system; and (iii)acquire an additional image signal block either before the longitudinalT2 encoding pulse sequence or following the acquiring of the postlongitudinal T2 encoding pulse sequence image signal block using the RFsystem. In addition, the routines are structured and configured togenerate calculated image data based on at least the post longitudinalT2 encoding pulse sequence image signal block using a self-correctingnormalization image combination scheme.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an MRI system according to an exemplaryembodiment in which the various embodiments of the methods describedherein may be implemented;

FIG. 2 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a first exemplaryembodiment of the disclosed concept;

FIG. 3 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a second exemplaryembodiment of the disclosed concept;

FIG. 4 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a third exemplaryembodiment of the disclosed concept;

FIG. 5 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a fourth exemplaryembodiment of the disclosed concept;

FIG. 6 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a fifth exemplaryembodiment of the disclosed concept; and

FIG. 7 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a sixth exemplaryembodiment of the disclosed concept.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As used herein, the singular form of “a”, “an”, and “the” include pluralreferences unless the context clearly dictates otherwise.

As used herein, the statement that two or more parts or components are“coupled” shall mean that the parts are joined or operate togethereither directly or indirectly, i.e., through one or more intermediateparts or components, so long as a link occurs.

As used herein, the term “number” shall mean one or an integer greaterthan one (i.e., a plurality).

As used herein, the term “inner product normalization (IPN) imagecombination” shall mean the combination of two MRI images usingself-correcting normalization using the following:

$R = {{real}\mspace{14mu} \left( \frac{S_{1}^{*}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right)}$

where S₁ and S₂ are the GRE signal at inversion recovery delays TI1 andTI2, respectively, and the ‘*’ operator is a complex conjugator, asdescribed in, for example, Marques J, Kober T, Krueger G, van der ZwaagW, Van de Moortele P, Gruetter R., “MP2RAGE, a self bias-field correctedsequence for improved segmentation and T1 mapping at high field”,Neuroimage 2010 49:1271-81.

As used herein, the term “sign inverted inner product normalization(−IPN) image combination” shall mean an IPN image combination wherein inthe equation of self-normalization, the “S₁*S₂” term is replaced by“−S1*S2”.

As used herein, the term “spin echo pulse sequence” shall mean an MRIpulse sequence that includes a 90 degree RF pulse followed by one ormore 180 degree refocusing RF pulses and optionally one or moreadditional 90 degree RF pulses.

As used herein, the term “inversion pulse sequence” shall mean an MRIpulse sequence used to invert the signal prior to a spin echo pulsesequence.

Directional phrases used herein, such as, for example and withoutlimitation, top, bottom, left, right, upper, lower, front, back, andderivatives thereof, relate to the orientation of the elements shown inthe drawings and are not limiting upon the claims unless expresslyrecited therein.

The disclosed concept will now be described, for purposes ofexplanation, in connection with numerous specific details in order toprovide a thorough understanding of the subject innovation. It will beevident, however, that the disclosed concept can be practiced withoutthese specific details without departing from the spirit and scope ofthis innovation.

As described in greater detail herein, the disclosed concept provides anew MRI pulse sequence and associated methods to generate controlled T1and T2 weighted images in an SAR efficient manner. Using a transceiverarray, this sequence overcomes the SAR problems of existing methods togenerate images with better than 0.7×0.7×1.2 mm resolution throughintegration of a T2 preparation spin echo into a multi-block inversionrecovery sequence. With a self-correcting image combination strategybased on sign inverted inner product normalization (−IPN) imagecombination and/or inner product normalization (IPN) image combination,the acquisition scheme of the disclosed concept works to detect long T2components while suppressing cerebral spinal fluid (CSF), which has beena problem for 7T imaging. The flexibility of the sequence of thedisclosed concept permits quantitation of T1 and T2 which forms thebasis for high efficiency imaging. The methods of the disclosed conceptare referred to herein as magnetization prepared fluid attenuatedinversion recovery gradient echo (MPFLAGRE).

FIG. 1 is a schematic diagram of an MRI system 2 according to anexemplary embodiment in which the various embodiments of the methodsdescribed herein may be implemented. In particular, the methodsdescribed herein, in the various embodiments, may be implemented as anumber of software routines embedded in the control system of MRI system2. Referring to FIG. 1, MRI system 2 includes a table 4 on which apatient 6 rests. Table 4 is structured to slide inside a tunnel 7 formedby a housing 8. Housing 8 houses a superconducting magnet 10, whichgenerates a very high magnetic field. Housing 8 also houses a gradientcoil 12. Gradient coil 12 is integrated with magnet 10 for adjusting themagnetic field. Housing 8 further houses a Radio Frequency (RF) assemblyor system 14, which applies RF pulses to a specific body-part of thepatient 6 to be analyzed, and receives signals that are returned by thesame body-part. RF assembly or system 14 may be, for example, a surfacecoil system, a saddle coil system, a Helmholtz coil system, an RFtransceiver array system, or any other suitable RF system or structure.A magnetic shield is provided, which surrounds magnet 10, gradient coil12 and RF system 14, and which minimizes the magnetic fields generatedwithin tunnel 7 from radiating outside the room in which MRI system 2 islocated (the magnet shield usually encompasses the entire room).Magnetic shield also protects the inside of tunnel 7 from externalmagnetic interferences.

MRI system 2 also includes a control module 18 that includes all thecomponents that are required to drive gradient coil system 12 and RFsystem 14 (for example, an RF transmitter, an output amplifier, and thelike); control module 18 also includes all the components that arerequired to acquire the response signals from the body-part (forexample, an input amplifier, an Analog-To-Digital Converter, or ADC, andthe like). Moreover, control module 18 drives an optional motor (notshown) that is used to move the table 4 to and from tunnel 7. Finally,control module 18 includes a processing portion which may be, forexample, a microprocessor, a microcontroller or some other suitableprocessing device, and a memory portion that may be internal to theprocessing portion or operatively coupled to the processing portion andthat provides a storage medium for data and software executable by theprocessing portion for controlling the operation of MRI system 2,including the routines for implementing the various embodiments of themethod described herein.

MRI system 2 further includes a computer system 20 (for example, aPersonal Computer, or PC), which is coupled to control module 18.Computer system 20 is configured to control MRI system 2 and topost-process the acquired response signals. Computer system 20 is alsoconfigured to display images relating to the body-part under analysis.In an alternative embodiment, one or more of the routines forimplementing the various embodiments of the method described herein maybe implemented in and by computer system 20.

FIG. 2 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a first exemplaryembodiment of the disclosed concept. The embodiment shown in FIG. 2 isreferred to as MPFLAGRE-2 herein because it involves the acquisition oftwo image signal blocks following a longitudinal T2 encoding pulsesequence. For illustrative purposes, the method will be described inconnection with the exemplary MRI system 2 shown in FIG. 1, although itwill be appreciated that other implementations and configurations arepossible within the scope of the disclosed concept.

Referring to FIG. 2, the method begins at step 100, wherein an inversionpulse sequence is performed by MRI system 2. Next, at step 105, alongitudinal T2 encoding pulse sequence is performed by MRI system 2. Inthe exemplary embodiment, the longitudinal T2 encoding pulse sequence ofstep 105 is a spin echo pulse sequence. In one particularimplementation, the spin echo pulse sequence is a non-selective spinecho pulse sequence of duration TE comprising the following format:90x+−180−180−90x−. After step 105, the method proceeds to step 110. Atstep 110, MRI system 2 acquires a first image signal block (S₁) atinversion recovery delay time TI1. Then, at step 115, MRI system 2acquires a second image signal block (S₂) at inversion recovery delaytime TI2. In the exemplary embodiment, S₁ and S₂ are each a 3D gradientrecalled echo (GRE) readout block. Then, at step 120, MRI system 2generates calculated image data based on an −IPN image combination of S₁and S₂ including a sign inversion of S₁. Specifically, the calculatedimage data is R_(1/2), with R_(1/2) being calculated based on thefollowing:

$R_{1/2} = {{real}\mspace{14mu} {\left( \frac{{- S_{1}^{*}}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right).}}$

FIG. 3 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a second exemplaryembodiment of the disclosed concept. The embodiment shown in FIG. 3 isreferred to as MPFLAGRE-3 herein because it involves the acquisition ofthree image signal blocks following a longitudinal T2 encoding pulsesequence. For illustrative purposes, the method will be described inconnection with the exemplary MRI system 2 shown in FIG. 1, although itwill be appreciated that other implementations and configurations arepossible within the scope of the disclosed concept.

Referring to FIG. 3, the method begins at step 200, wherein an inversionpulse sequence is performed by MRI system 2. Next, at step 205, alongitudinal T2 encoding pulse sequence as described herein is performedby MRI system 2. After step 205, the method proceeds to step 210. Atstep 210, MRI system 2 acquires a first image signal block (S₁) atinversion recovery delay time TI1. Then, at step 215, MRI system 2acquires a second image signal block (S₂) at inversion recovery delaytime TI2, and at step 220, MRI system 2 acquires a third image signalblock (S₃) at inversion recovery delay time TI3. In the exemplaryembodiment, S₁, S₂ and S₃ are each a 3D gradient recalled echo (GRE)readout block. Then, at step 225, MRI system 2 generates calculatedimage data based on: (i) a −IPN image combination of S₁ and S₃ includinga sign inversion of S₁, wherein the calculated image data is R_(1/3),with R_(1/3) being calculated based on the following:

${R_{1/3} = {{real}\mspace{14mu} \left( \frac{{- S_{1}^{*}}S_{3}}{{S_{1}}^{2} + {S_{3}}^{2}} \right)}},$

and/or (ii) a −IPN image combination of (S₁+S₂) and S₃ including a signinversion of (S₁+S₂), wherein the calculated image data is R_((1+2)/3),with R_((1+2)/3) being calculated based on the following:

$R_{{({1 + 2})}/3} = {{real}\mspace{14mu} {\left( \frac{{- \left( {S_{1} + S_{2}} \right)^{*}}S_{3}}{{{S_{1} + S_{2}}}^{2} + {S_{3}}^{2}} \right).}}$

FIG. 4 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a third exemplaryembodiment of the disclosed concept. The embodiment shown in FIG. 4 isreferred to as MPFLAGRE-4 herein because it involves the acquisition offour image signal blocks following a longitudinal T2 encoding pulsesequence. For illustrative purposes, the method will be described inconnection with the exemplary MRI system 2 shown in FIG. 1, although itwill be appreciated that other implementations and configurations arepossible within the scope of the disclosed concept Referring to FIG. 4,the method begins at step 300, wherein an inversion pulse sequence isperformed by MRI system 2. Next, at step 305, a longitudinal T2 encodingpulse sequence as described herein is performed by MRI system 2. Afterstep 305, the method proceeds to step 310. At step 310, MRI system 2acquires a first image signal block (S₁) at inversion recovery delaytime TI1. Then, at step 315, MRI system 2 acquires a second image signalblock (S₂) at inversion recovery delay time TI2, at step 320, MRI system2 acquires a third image signal block (S₃) at inversion recovery delaytime TI3, and at step 325, MRI system 2 acquires a fourth image signalblock (S₄) at inversion recovery delay time TI4. In the exemplaryembodiment, S₁, S₂, S₃ and S₄ are each a 3D gradient recalled echo (GRE)readout block. Then, at step 330, MRI system 2 generates calculatedimage data based on: (i) a −IPN image combination of S₁ and S₄ includinga sign inversion of S₁, wherein the calculated image data is R_(1/4),with R_(1/4) being calculated based on the following:

${R_{1/4} = {{real}\mspace{14mu} \left( \frac{{- S_{1}^{*}}S_{4}}{{S_{1}}^{2} + {S_{4}}^{2}} \right)}},$

and/or (ii) a −IPN image combination of (S₁+S₂) and S₄ including a signinversion of (S₁+S₂), wherein the calculated image data is R_((1+2)/4),with R_((1+2)/4) being calculated based on the following:

$R_{{({1 + 2})}/4} = {{real}\mspace{14mu} {\left( \frac{{- \left( {S_{1} + S_{2}} \right)^{*}}S_{4}}{{{S_{1} + S_{2}}}^{2} + {S_{4}}^{2}} \right).}}$

In this exemplary embodiment, MRI system 2 may also simultaneouslygenerate Ru; and R_((1+2)/3) as described above.

FIG. 5 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a fourth exemplaryembodiment of the disclosed concept. The embodiment shown in FIG. 5 isreferred to as MPFLAGRE-2L herein because it involves the acquisition oftwo blocks with the longitudinal T2 encoding pulse sequence applied latein the inversion recovery. For illustrative purposes, the method will bedescribed in connection with the exemplary MRI system 2 shown in FIG. 1,although it will be appreciated that other implementations andconfigurations are possible within the scope of the disclosed concept.

Referring to FIG. 5, the method begins at step 400, wherein an inversionpulse sequence is performed by MRI system 2. Next, at step 405, MRIsystem 2 acquires a first image signal block (S₁) at inversion recoverydelay time TI1. Next, at step 410, a longitudinal T2 encoding pulsesequence as described herein is performed by MRI system 2. After step410, the method proceeds to step 415. Then, at step 415, MRI system 2acquires a second image signal block (S₂) at inversion recovery delaytime TI2. In the exemplary embodiment, S₁ and S₂ are each a 3D gradientrecalled echo (GRE) readout block. Then, at step 420, MRI system 2generates calculated image data based on the inner product normalizationof S₁ and S₂, wherein the calculated image data is R_(1/2), and whereinR_(1/2) is calculated based on the following:

$R_{1/2} = {{real}\mspace{14mu} {\left( \frac{{- S_{1}^{*}}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right).}}$

FIG. 6 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a fifth exemplaryembodiment of the disclosed concept. The embodiment shown in FIG. 6 isreferred to as MPFLAGRE-3L herein because it involves the acquisition ofthree image signal blocks, with the T2 encoding module applied late inthe inversion recovery. For illustrative purposes, the method will bedescribed in connection with the exemplary MRI system 2 shown in FIG. 1,although it will be appreciated that other implementations andconfigurations are possible within the scope of the disclosed concept.

Referring to FIG. 6, the method begins at step 500, wherein an inversionpulse sequence is performed by MRI system 2. Next, at step 505, MRIsystem 2 acquires a first image signal block (S₁) at inversion recoverydelay time TI1. Next, at step 510, a longitudinal T2 encoding pulsesequence as described herein is performed by MRI system 2. After step510, the method proceeds to step 515. Then, at step 515, MRI system 2acquires a second image signal block (S₂) at inversion recovery delaytime TI2, and then at step 520, MRI system 2 acquires a third imagesignal block (S₃) at inversion recovery delay time TI3. In the exemplaryembodiment, S₁, S₂ and S₃ are each a 3D gradient recalled echo (GRE)readout block. Then, at step 525, MRI system 2 generates calculatedimage data based on the inner product normalization combination of S₂and S₁, wherein the calculated image data is R_(2/1), and whereinR_(2/1) is calculated based on the following:

${R_{2/1} = {{real}\mspace{14mu} \left( \frac{S_{2}^{*}S_{1}}{{S_{2}}^{2} + {S_{1}}^{2}} \right)}},$

and/or (ii) an inner product normalization combination of (S₃+S₂) and S₁wherein the calculated image data is R_((3+2)/1), and whereinR_((3+2)/1) is calculated based on the following:

$R_{{({3 + 2})}/1} = {{real}\mspace{14mu} {\left( \frac{\left( {S_{3} + S_{2}} \right)^{*}S_{1}}{{{S_{3} + S_{2}}}^{2} + {S_{1}}^{2}} \right).}}$

FIG. 7 is a flowchart showing a method of generating T1 and T2 weightedmagnetic resonance imaging data according to a sixth exemplaryembodiment of the disclosed concept. The embodiment shown in FIG. 7 isreferred to as MPFLAGRE-4L herein because it involves the acquisition offour image signal blocks with the longitudinal T2 encoding pulsesequence applied late after the inversion. For illustrative purposes,the method will be described in connection with the exemplary MRI system2 shown in FIG. 1, although it will be appreciated that otherimplementations and configurations are possible within the scope of thedisclosed concept.

Referring to FIG. 7, the method begins at step 600, wherein an inversionpulse sequence is performed by MRI system 2. Next, at step 605, MRIsystem 2 acquires a first image signal block (S₁) at inversion recoverydelay time TI1. At step 610, MRI system 2 acquires a second image signalblock (S₂) at inversion recovery delay time TI2. Then, at step 615, alongitudinal T2 encoding pulse sequence as described herein is performedby MRI system 2. After step 615, the method proceeds to step 620. Atstep 620, MRI system 2 acquires image signal block (S₃) at inversionrecovery delay time TI3. Then, at step 625, MRI system 2 acquires afourth image signal block (S₄) at inversion recovery delay time TI4. Inthe exemplary embodiment, S₁, S₂, S₃ and S₄ are each a 3D gradientrecalled echo (GRE) readout block. Then, at step 630, MRI system 2generates calculated image data based on: (i) an IPN image combinationof S₁ and S₃ wherein the calculated image data is R_(3/1), and whereinR_(3/1) is calculated based on the following:

${R_{3/1} = {{real}\mspace{14mu} \left( \frac{S_{3}^{*}S_{1}}{{S_{3}}^{2} + {S_{1}}^{2}} \right)}},$

and/or (ii) an IPN image combination of (S₃+S₄) and S₁ wherein thecalculated image data is R_((3+4)/1), and wherein R_((3+4)/1) iscalculated based on the following:

$R_{{({3 + 4})}/1} = {{real}\mspace{14mu} {\left( \frac{\left( {S_{3} + S_{4}} \right)^{*}S_{1}}{{{S_{3} + S_{4}}}^{2} + {S_{1}}^{2}} \right).}}$

In this exemplary embodiment, MRI system 2 may also simultaneouslygenerate R_(3/1) and R_((3+2)/1) as described above.

While the exemplary methods described herein include performing only asingle longitudinal T2 encoding pulse sequence during the inversionrecovery period, it will be appreciated that multiple longitudinal T2encoding pulse sequences may also be employed within the scope of thedisclosed concept.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The word “comprising” or “including”does not exclude the presence of elements or steps other than thoselisted in a claim. In a device claim enumerating several means, severalof these means may be embodied by one and the same item of hardware. Theword “a” or “an” preceding an element does not exclude the presence of aplurality of such elements. In any device claim enumerating severalmeans, several of these means may be embodied by one and the same itemof hardware. The mere fact that certain elements are recited in mutuallydifferent dependent claims does not indicate that these elements cannotbe used in combination.

Although the invention has been described in detail for the purpose ofillustration based on what is currently considered to be the mostpractical and preferred embodiments, it is to be understood that suchdetail is solely for that purpose and that the invention is not limitedto the disclosed embodiments, but, on the contrary, is intended to covermodifications and equivalent arrangements that are within the spirit andscope of the appended claims. For example, it is to be understood thatthe present invention contemplates that, to the extent possible, one ormore features of any embodiment can be combined with one or morefeatures of any other embodiment.

What is claimed is:
 1. A magnetic resonance imaging (MRI) method,comprising: performing an inversion pulse sequence using an MRI system,the inversion pulse sequence producing an inversion recovery period;during the inversion recovery period: (i) performing a longitudinal T2encoding pulse sequence using the MRI system; (ii) acquiring a postlongitudinal T2 encoding pulse sequence image signal block immediatelyfollowing the longitudinal T2 encoding pulse sequence using the MRIsystem; and (iii) acquiring an additional image signal block eitherbefore the longitudinal T2 encoding pulse sequence or following theacquiring of the post longitudinal T2 encoding pulse sequence imagesignal block using the MRI system; and generating calculated image databased on at least the post longitudinal T2 encoding pulse sequence imagesignal block using a self-correcting normalization image combinationscheme.
 2. The method according to claim 1, wherein the self-correctingnormalization image combination scheme includes an inner productnormalization image combination or a sign inverted inner productnormalization image combination.
 3. The method according to claim 1,wherein the post longitudinal T2 encoding pulse sequence image signalblock and the additional image signal block are each a 3D gradientrecalled echo (GRE) readout block.
 4. The method according to claim 1,wherein the longitudinal T2 encoding pulse sequence is a spin echo pulsesequence.
 5. The method according to claim 4, wherein the spin echopulse sequence is a non-selective spin echo pulse sequence of durationTE comprising the following format: 90x+−180−180−90x−.
 6. The methodaccording to claim 1, the post longitudinal T2 encoding pulse sequenceimage signal block is designated S₁ and the additional image signalblock is designated S₂, wherein (i), (ii) and (iii) comprise performingthe longitudinal T2 encoding pulse sequence immediately following theinversion pulse sequence, acquiring S₁ immediately following thelongitudinal T2 encoding pulse sequence, and acquiring S₂ following theacquiring of S₁.
 7. The method according to claim 6, wherein thegenerating the calculated image data is based on a sign inverted innerproduct normalization image combination of S₁ and S₂ including a signinversion of S₁, wherein the calculated image data is R_(1/2), andwherein R_(1/2) is calculated based on the following:$R_{1/2} = {{real}\mspace{14mu} {\left( \frac{{- S_{1}^{*}}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right).}}$8. The method according to claim 6, further comprising acquiring a thirdimage signal block (S₃) following the acquiring of S₂ using the MRIsystem, wherein the generating the calculated image data is based on asign inverted inner product normalization image combination of S₁ and S₃including a sign inversion of S₁, wherein the calculated image data isR_(1/3), and wherein R_(1/3) is calculated based on the following:$R_{1/3} = {{real}\mspace{14mu} {\left( \frac{{- S_{1}^{*}}S_{3}}{{S_{1}}^{2} + {S_{3}}^{2}} \right).}}$9. The method according to claim 6, further comprising acquiring a thirdimage signal block (S₃) following the acquiring of S₂ using the MRIsystem and acquiring a fourth image signal block (S₄) following theacquiring of S₃ using the MRI system, wherein the generating thecalculated image data is based on a sign inverted inner productnormalization image combination of S₁ and S₄ including a sign inversionof S₁, wherein the calculated image data is R_(1/4), and wherein R_(1/4)is calculated based on the following:$R_{1/4} = {{real}\mspace{14mu} {\left( \frac{{- S_{1}^{*}}S_{4}}{{S_{1}}^{2} + {S_{4}}^{2}} \right).}}$10. The method according to claim 6, further comprising acquiring athird image signal block (S₃) following the acquiring of S₂ using theMRI system, wherein the generating the calculated image data is based ona sign inverted inner product normalization image combination of (S₁+S₂)and S₃ including a sign inversion of (S₁+S₂), wherein the calculatedimage data is R_((1+2)/3), and wherein R_((1+2)/3) is calculated basedon the following:$R_{{({1 + 2})}/3} = {{real}\mspace{14mu} {\left( \frac{{- \left( {S_{1} + S_{2}} \right)^{*}}S_{3}}{{{S_{1} + S_{2}}}^{2} + {S_{3}}^{2}} \right).}}$11. The method according to claim 6, further comprising acquiring athird image signal block (S₃) following the acquiring of S₂ using theMRI system and acquiring a fourth image signal block (S₄) following theacquiring of S₃ using the MRI system, wherein the generating thecalculated image data is based on a sign inverted inner productnormalization image combination of (S₁+S₂) and S₄ including a signinversion of (S₁+S₂), wherein the calculated image data is R_((1+2)/4),and wherein R_((1+2)/4) is calculated based on the following:$R_{{({1 + 2})}/4} = {{real}\mspace{14mu} {\left( \frac{{- \left( {S_{1} + S_{2}} \right)^{*}}S_{4}}{{{S_{1} + S_{2}}}^{2} + {S_{4}}^{2}} \right).}}$12. The method according to claim 1, wherein the additional image signalblock is designated S₁ and the post longitudinal T2 encoding pulsesequence image signal block is designated S₂, wherein (i), (ii) and(iii) comprise acquiring S₁ before performing the longitudinal T2encoding pulse sequence, and acquiring S₂ immediately following thelongitudinal T2 encoding pulse sequence.
 13. The method according toclaim 12, wherein the generating the calculated image data is based onan inner product normalization image combination of S₁ and S₂, whereinthe calculated image data is R_(1/2), and wherein R_(1/2) is calculatedbased on the following:$R_{1/2} = {{{real}\left( \frac{S_{1}^{*}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right)}.}$14. The method according to claim 12, further comprising acquiring athird image signal block (S₃) following the acquiring of S₂ using theMRI system, wherein the generating the calculated image data is based onan inner product normalization image combination of S₂ and S₁, whereinthe calculated image data is R_(2/1), and wherein R_(2/1) is calculatedbased on the following:${R_{2/1} = {{real}\left( \frac{S_{2}^{*}S_{1}}{{S_{2}}^{2} + {S_{1}}^{2}} \right)}},$and/or wherein the generating the calculated image data is based on aninner product normalization image combination of (S₃+S₂) and S₁ whereinthe calculated image data is R_((3+2)/1), and wherein R_((3+2)/1) iscalculated based on the following:$R_{{({3 + 2})}/1} = {{{real}\left( \frac{\left( {S_{3} + S_{2}} \right)*S_{1}}{{{S_{3} + S_{2}}}^{2} + {S_{1}}^{2}} \right)}.}$15. The method according to claim 12, further comprising acquiring athird image signal block (S₃) following the acquiring of S₂ using theMRI system and acquiring a fourth image signal block (S₄) following theacquiring of S₃ using the MRI system, wherein the generating thecalculated image data is based on an inner product normalization imagecombination of S₁ and S₃ wherein the calculated image data is R_(3/1),and wherein R_(3/1) is calculated based on the following:${R_{3/1} = {{real}\left( \frac{S_{3}^{*}S_{1}}{{S_{3}}^{2} + {S_{1}}^{2}} \right)}},$and/or wherein the generating the calculated image data is based on anIPN image combination of (S₃+S₄) and S₁ wherein the calculated imagedata is R_((3+4)/1), and wherein R_((3+4)/1) is calculated based on thefollowing:$R_{{({3 + 4})}/1} = {{{real}\left( \frac{\left( {S_{3} + S_{4}} \right)*S_{1}}{{{S_{3} + S_{4}}}^{2} + {S_{1}}^{2}} \right)}.}$16. A non-transitory computer readable medium storing one or moreprograms, including instructions, which when executed by a computer,causes the computer to perform the method of claim
 1. 17. A magneticresonance imaging (MRI) system, comprising: a magnet; an RF system; anda control system, wherein the control system stores and is structuredand configured to execute a number of routines, the number of routinesbeing structured and configured to: perform an inversion pulse sequenceusing the RF system, the inversion pulse sequence producing an inversionrecovery period; during the inversion recovery period: (i) perform alongitudinal T2 encoding pulse sequence using the RF system; (ii)acquire a post longitudinal T2 encoding pulse sequence image signalblock immediately following the longitudinal T2 encoding pulse sequenceusing the RF system; and (iii) acquire an additional image signal blockeither before the longitudinal T2 encoding pulse sequence or followingthe acquiring of the post longitudinal T2 encoding pulse sequence imagesignal block using the RF system; and generate calculated image databased on at least the post longitudinal T2 encoding pulse sequence imagesignal block using a self-correcting normalization image combinationscheme.
 18. The MRI system according to claim 17, wherein theself-correcting normalization image combination scheme includes an innerproduct normalization image combination or a sign inverted inner productnormalization image combination.
 19. The MRI system according to claim17, wherein the post longitudinal T2 encoding pulse sequence imagesignal block and the additional image signal block are each a 3Dgradient recalled echo (GRE) readout block.
 20. The MRI system accordingto claim 17, wherein the longitudinal T2 encoding pulse sequence is aspin echo pulse sequence.
 21. The MRI system according to claim 17,wherein the spin echo pulse sequence is a non-selective spin echo pulsesequence of duration TE comprising the following format:90x+−180−180−90x−.
 22. The MRI system according to claim 17, the postlongitudinal T2 encoding pulse sequence image signal block is designatedS₁ and the additional image signal block is designated S₂, wherein (i),(ii) and (iii) comprise performing the longitudinal T2 encoding pulsesequence immediately following the inversion pulse sequence, acquiringS₁ immediately following the longitudinal T2 encoding pulse sequence,and acquiring S₂ following the acquiring of S₁.
 23. The MRI systemaccording to claim 22, wherein the calculated image data is generatedbased on a sign inverted inner product normalization image combinationof S₁ and S₂ including a sign inversion of S₁, wherein the calculatedimage data is R_(1/2), and wherein R_(1/2) is calculated based on thefollowing:$R_{1/2} = {{{real}\left( \frac{{- S_{1}^{*}}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right)}.}$24. The MRI system according to claim 22, the number of routines beingfurther structured and configured to acquire a third image signal block(S₃) following the acquiring of S₂ using the RF system, wherein thegenerating the calculated image data is based on a sign inverted innerproduct normalization image combination of S₁ and S₃ including a signinversion of S₁, wherein the calculated image data is R_(1/3), andwherein R_(1/3) is calculated based on the following:$R_{1/3} = {{{real}\left( \frac{{- S_{1}^{*}}S_{3}}{{S_{1}}^{2} + {S_{3}}^{2}} \right)}.}$25. The MRI system according to claim 22, the number of routines beingfurther structured and configured to acquire a third image signal block(S₃) following the acquiring of S₂ using the RF system and acquire afourth image signal block (S₄) following the acquiring of S₃ using theRF system, wherein the calculated image data is generated based on asign inverted inner product normalization image combination of S₁ and S₄including a sign inversion of S₁, wherein the calculated image data isR_(1/4), and wherein R_(1/4) is calculated based on the following:$R_{1/4} = {{{real}\left( \frac{{- S_{1}^{*}}S_{4}}{{S_{1}}^{2} + {S_{4}}^{2}} \right)}.}$26. The MRI system according to claim 22, the number of routines beingfurther structured and configured to acquire a third image signal block(S₃) following the acquiring of S₂ using the RF system, wherein thecalculated image data is generated based on a sign inverted innerproduct normalization image combination of (S₁+S₂) and S₃ including asign inversion of (S₁+S₂), wherein the calculated image data isR_((1+2)/3), and wherein R_((1+2)/3) is calculated based on thefollowing:$R_{{({1 + 2})}/3} = {{{real}\left( \frac{{- \left( {S_{1} + S_{2}} \right)}*S_{3}}{{{S_{1} + S_{2}}}^{2} + {S_{3}}^{2}} \right)}.}$27. The MRI system according to claim 22, the number of routines beingfurther structured and configured to acquire a third image signal block(S₃) following the acquiring of S₂ using the RF system and acquire afourth image signal block (S₄) following the acquiring of S₃ using theRF system, wherein the calculated image data is generated based on asign inverted inner product normalization image combination of (S₁+S₂)and S₄ including a sign inversion of (S₁+S₂), wherein the calculatedimage data is R_((1+2)/4), and wherein R_((1+2)/4) is calculated basedon the following:$R_{{({1 + 2})}/4} = {{{real}\left( \frac{{- \left( {S_{1} + S_{2}} \right)}*S_{4}}{{{S_{1} + S_{2}}}^{2} + {S_{4}}^{2}} \right)}.}$28. The MRI system according to claim 17, wherein the additional imagesignal block is designated S₁ and the post longitudinal T2 encodingpulse sequence image signal block is designated S₂, wherein (i), (ii)and (iii) comprise acquiring S₁ before performing the longitudinal T2encoding pulse sequence, and acquiring S₂ immediately following thelongitudinal T2 encoding pulse sequence.
 29. The MRI system according toclaim 28, wherein the generating the calculated image data is based onan inner product normalization image combination of S₁ and S₂, whereinthe calculated image data is R_(1/2), and wherein R_(1/2) is calculatedbased on the following:$R_{1/2} = {{{real}\left( \frac{S_{1}^{*}S_{2}}{{S_{1}}^{2} + {S_{2}}^{2}} \right)}.}$30. The MRI system according to claim 28, the number of routines beingfurther structured and configured to acquire a third image signal block(S₃) following the acquiring of S₂ using the MRI system, wherein thegenerating the calculated image data is based on an inner productnormalization image combination of S₂ and S₁, wherein the calculatedimage data is R_(2/1), and wherein R_(2/1) is calculated based on thefollowing:${R_{2/1} = {{real}\left( \frac{S_{2}^{*}S_{1}}{{S_{2}}^{2} + {S_{1}}^{2}} \right)}},$and/or wherein the generating the calculated image data is based on aninner product normalization image combination of (S₃+S₂) and S₁ whereinthe calculated image data is R_((3+2)/1), and wherein R_((3+2)/1) iscalculated based on the following:$R_{{({3 + 2})}/1} = {{{real}\left( \frac{\left( {S_{3} + S_{2}} \right)*S_{1}}{{{S_{3} + S_{2}}}^{2} + {S_{1}}^{2}} \right)}.}$31. The MRI system according to claim 28, the number of routines beingfurther structured and configured to acquire a third image signal block(S₃) following the acquiring of S₂ using the MRI system and acquiring afourth image signal block (S₄) following the acquiring of S₃ using theMRI system, wherein the generating the calculated image data is based onan inner product normalization image combination of S₁ and S₃ whereinthe calculated image data is R %, and wherein R₃n is calculated based onthe following:${R_{3/1} = {{real}\left( \frac{S_{3}^{*}S_{1}}{{S_{3}}^{2} + {S_{1}}^{2}} \right)}},$and/or wherein the generating the calculated image data is based on anIPN image combination of (S₃+S₄) and S₁ wherein the calculated imagedata is R_((3+4)/1), and wherein R_((3+4)/1) is calculated based on thefollowing:$R_{{({3 + 4})}/1} = {{{real}\left( \frac{\left( {S_{3} + S_{4}} \right)*S_{1}}{{{S_{3} + S_{4}}}^{2} + {S_{1}}^{2}} \right)}.}$